Alphanumeric character display and waveform generator therefor

ABSTRACT

Electrical waveforms of arbitrary shape are generated by pulsing a delay line and taking a signal from the line via conductive strips of varying width mounted parallel to the line and capacitively coupled to it. The signal variation with time corresponds to the variation of effective capacitance as the energizing pulse is propagated along the delay line. With strips suitably contoured, the waveforms may be applied to the orthogonal deflecting electrodes of a cathode ray tube to trace any desired character on the tube screen. For example, a font of 96 characters can be made available with three delay lines carrying strips formed by printed circuit techniques and controlled by relatively simple selection circuits. Described sampling techniques permit indefinite expansion of the time base of developed waveforms.

United States Patent Sept. 5, 1972 [54] ALPHANUMERIC CHARACTER DISPLAYAND WAVEFORM GENERATOR THEREFOR [72] Inventor: Robert S. Harp, 166Merrill Ave.,

Sierra Madre, Calif. 91024 [22] Filed: April-8, 1970 [21] Appl. No.:26,495

52 US. 01.... ..340/324 A, 315/18 51 Int. Cl ..G06f 3/14 [58] FieldofSearch 40/324 A; 315/18, 30

[56] References Cited UNITED sTATEs PATENTS 2,525,893 10/1950 Gloess..340/324 A 3,289,195 11/1966 Townsend ..340/324 A 3,103,658 9/1963Chiang ..340/324 A 3,169,240 2/1965 Macovski ..340/324 A 3,609,744.9/1971 Pearson ..340/324 A Primary Examiner-Thomas B. HabeckerAssistant Examiner-Marshall M. Curtis Attorney-Charlton M. Lewis [57]ABSTRACT Electrical waveforms of arbitrary shape are generated bypulsing a delay line and taking a signal from the line via conductivestrips of varying width mounted parallel to the line and capacitivelycoupled to it. The signal variation with time corresponds to thevariation of effective capacitance as the energizing pulse is propagatedalong the delay line. With strips suitably contoured, the waveforms maybe applied to the orthogonal deflecting electrodes of a cathode ray tubeto trace any desired character on the tube screen. For example, a fontof 96 characters can bemade available with three delay lines carryingstrips formed by printed circuit techniques and controlled by relativelysimple selection circuits. Described sampling techniques permitindefinite expansion of the time base of developed waveforms.

4 Claims, 11 Drawing Figures CXI- CZZ

PATENTEDSEP 5 I972 SHEET 3 UF 3 ALPl-IANUMERIC CHARACTER DISPLAY ANDWAVEFORM GENERATOR THEREFOR This invention relates generally to thegeneration of electrical waveforms of arbitrary shape.

Such waveforms are useful for many purposes, including, in particular,the production of selected alphanumeric characters on the screen of acathode ray tube. For the sake of clarity, the invention will bedescribed primarily with relation to such character generation, butwithout implying limitation of the invention to that particular use. a

A primary object of the present invention is to permit economical andconvenient generation of a wide variety of waveforms of arbitrary shape,free from the artificial shape limitations that are inherent in most.

previously available methods of waveform generation.

A further object of the invention is to provide waveform generatingmechanism that is sufficiently economical and compact to make feasiblethe provision of a large vocabulary of relatively complex waveforms.

In the particular field of character generation, the in- .ventionpermits each character to be displayed on a Present electronic characterdisplay systems' generally provide means for tracing a limited varietyof fixed character components, such as dots or line segments. A desiredcharacter is then approximated by assembling selected components.Characters may be produced, for example, by selective display of certaindots of arectangular array, or certain line segments of a pattern.

The present invention, on the other hand, forms each characterindependently, with specially generated waveforms designed explicitlyfor that character. That approach not only permits complete freedom indesigning each character. It also permits great simplification of theusual circuitry for selecting a desired character from the font ofavailable characters. In accordance with the present invention,selection of a character requires in principle only the operation of asingle switch for directing an energizing pulse to the waveformdelineating mechanism for the desired character.

Waveform generating mechanisms in accordance with the invention areeconomical to fabricate, structurally simple and compact, and bothconvenient and and an output signal is taken from the line via circuitmeans capacitively coupled to the line, typically along its entirelength, the strength of coupling varying along the line in a mannercorresponding to the desired I waveform.

describes a method of generating alphanumeric charac-- I ters withwaveforms derived from a delay line by output windings inductivelycoupled to the line. However, the structures described by Townsend areinherently cumbersome in form and would be difiicult and expensive tofabricate. The present invention overcomes those difficulties by the useof capacitive coupling and by providing structuralfeat'ures, to bedescribed, which are made possible by such coupling.

The invention may utilize any form of 'delay line in which an inputelectrical pulse causesa charge to be propagated progressively along thelength of the line..A particularly suitable type of delay line comprisesa dielectric support form carrying'a helical winding of fine wire, withan electrically conductive ground plane capacitively coupledto thewinding. When an input pulse is supplied to one end of the winding andisabsorbed by a suitable terminating impedance at the other end, anelectrical charge is propagated with welldefined wave front along theline with a velocity determined by the parameters of the line. Thoseparameters include, in particular, the magnetic inductance of thewinding and the distributed capacitance between the electrical windingand the ground plane. The supporting form and the winding may becylindrical, but are preferably flat, so that the winding has twoessentially plane faces. 1

In accordance with the present invention adesired waveform may bederived from a delay line of the general typedescribed by mounting astrip-of conductive material parallel to the, line in mutuallyinsulated, capacitive relation to it. The width of the strip isnonuniform, varying in such a way that the capacitance per unit lengthbetween the'strip and the delay line varies along the line as a functionof the desired waveform. That capacitance variation may be gradual orstepwise. Several such strips are typically provided, each contoured toprovide a distinct waveform, and mounted in closely adjacent relationopposing a face of the delay line.

As the wavefront from the input pulse travels along the delay line, acharge is induced in the adjacent portion of each of the strips. Themagnitude of the charge appearing on each strip varies in directproportion to the width of the strip at the point directly adjacent thewavefront. Hence the signal taken from a strip displays a definite timevariation. The time component of that variation depends upon the speedof propagation of the delay line, while the amplitude of the variationis controllable by the contour of the strip.

The actual waveform obtained depends also upon the form of theenergizing pulse applied to the delay line. For example, energization bya step voltage complementary strips are coupled to the respective inputterminals of a differential amplifier or its equivalent, so that bothpositiveand negative-going portions of an output waveform aresymmetrically driven.

, In accordance with a further aspect of the invention, each outputstrip takes the place of a portion of the ground plane of the delayline. In fact, the entire area of the ground plane, ora major fractionof it, is typically split into a multiplicity of generally parallelstrips that the xor the y-component of the movement the same outputstrip-may be used for sucha group of characters. Also, for somecharacters the y-axis can be generated as described, and a conventionaltime base used for the x-axis. However, in view of the great economyinherent in the present waveform generating structure, it will usuallybe more economical to provide separate strips for each character than toconstruct the additional selection circuits required for reducing thenumber of strips.

A particular advantage of the invention is that, so

long as the cooperating waveforms for each character are derived fromthe same delay line, they are automatically developed in correct mutualphase relation.

The time base of waveforms developed in accordance with the inventioncan be varied considerably by suitable selection of the constants of thedelay line,

are mutually spaced by intervals just wide enough to in- I sure theirelectrical isolation. All of the strips are normally grounded. In orderto generate a selected. one of the available waveforms, thecorresponding strip is disconnected from ground and is coupled to anoutput circuit, all other strips remaining grounded. The

splittingof the ground plane into mutually insulated.

strips, and the isolation from ground of one strip, or 'of a smallnumber of strips, has no significant effect on the characteristics ofthe delay line. When the strips comprise pairs with complementary shapethey can utilize the entire ground plane. In any case, the strips canusually be shaped to nest in a manner to utilize most of the area of theground plane, any remaining areas being permanently grounded.

With the structure just described, selection of a particular waveformrequires only opening the circuit through which the selected strip isnormally connected to ground, and connecting the strip instead to theoutput circuit. The latter connection may employ capacitive coupling,and'no switching action is then required for it.

Each ground plane structure, embodying an array of output strips, istypically mounted on a support sheet of suitable dielectric material.The desired strip configuration can be reproduced on the sheet by use ofphotolithographic techniques and. materials familiar to those skilled inthe art of manufacturing printed circuit boards for electronic devices.Even 'highly intricate configurations can be produced by such techniquesat virtually any scale that may be desired, permitting one delay linestructure to generate selectivelyv a large number of distinct waveforms.A principal advantagev of the invention is the great ease and economywith which the described coupling structures can be fabricated.

When the generated waveforms are to be used for displaying alphanumericcharacters on a cathode 'ray tube, two strips are ordinarily requiredfor generating deflection waveforms for the xand y-coordiriates ofeachcharacter. A third strip may be provided for developing a gatingwaveform for control of the intensity of the cathode ray beam. Sinceseveral characters may movement, identical movement patterns for eitherfor example by winding the delayline on a form of fer 1 rite or othermagnetically permeable material to slow the propagation velocity of the.wave front. In accordance with a further aspect of the invention, thetime base of the generated waveforms may be expanded to any desiredextent by pulsing the delay line periodically and sampling the resultingseries of waveforms at progressively varying points. The sampled dataare then assembled with suitable filtering to reproduce the waveformwith time base corresponding to a complete cycle of sampling. With thatmodification, a character generating system in accordance with theinvention can drive the xand y-coordinates of a conventional penrecorder, for example, and is useful for drawing characters inconnection with known types of automatic drafting system.

A full understanding of the invention, and of its further objects andadvantages, will be had from the following description of certainillustrative manners of carrying it out. The particulars of thatdescription, and of the accompanying drawings whichform a part of it,are intended only as illustration and not as a limitation upon the scopeof the invention, which is defined in the appended claims. v

In the drawings: I FIG. 1 is a schematic perspective, partially brokenaway, representing an illustrative waveform generator in accordance withthe invention;

FIG. 2 is a transverse section corresponding generally to FIG. 1;

FIG. 3 is a longitudinal section on line 3-3 of FIG.

FIG. 4 is a schematic plan representing illustrative coupling strips,with schematic control circuits;

FIG. 5 is a simplified section corresponding to FIG. 3 and-representinga modification;

FIG. 6 is a section on line 6-6 of FIG. 5;

FIG. 7 is a graph showing an output waveform corresponding to FIG. 6;

FIG. 8 is a series of schematic graphs illustrating waveforms generatedunder varying conditions;

FIG. 9 is a schematic diagram of a control system in accordance with theinvention;

FIG. 10 is a schematic block diagram representing a system for expandinga waveform time base; and

FIG. 1 l is a schematic diagram representing a system employing acarrier frequency.

As represented schematically in FIGS. 1 to 3, the waveform generatingdevice comprises the flat delay line 23 with array 30 of couplingelements 32 for generating selectively any one of a plurality ofdistinct waveforms. Delay line 23 comprises the winding 24 of finecopper wire wound on the flat dielectric form 22 with the longitudinalaxis 21. Winding 24 is connected at one end to the input terminal 26and-at the other end to the output terminal 28, which is typicallyconnected to ground through a terminating resistance 29, suitablymatched to the characteristic impedance of the delay line to preventreflection of pulses propagated along the line. Suitable magneticallypermeable materials may be incorporated in form 22 for controlling thedelay time. The transverse dimensions and shape of form 22 areordinarily uniform throughout its length, but may be varied if desiredto obtain special effects in accordance with the known principles ofelectromagnetism. I v

The array 30 of coupling elements 32 is mounted in parallel, closelyspaced relation directly facingv the winding of the delay line. A secondcomplete assembly of coupling elements is typically mounted incorresponding relation to the other face of the delay line, as indicatedin fragmentary form at 30a in FIG. 1. Such a second array is omitted inFIGS. 2 and 3 for clarity of illustration, but is suggested byindication of the midplane 37 of the assembly. The coupling elements 32comprise thin strips of highly conductive material such as copper, andare typically deposited photolithographically in a predetermined patternon the inner face of the support layer 36 of dielectric material. Eachstrip typically extends essentially the entire length of the-delay line,and adjacent strips are spaced from each other by intervals 33 justsufficient to provide reliable insulation. The spacing of the entirearray of strips from the delay line winding is accurately defined by thesheet 34 of dielectric material such as polystyrene. The thickness ofthat sheet may vary in predetermined manner if desired, to produce acorresponding variation in capacitance, but will be assumed to beuniform for clarity of description. The entire assembly is shielded fromstray fields by the grounded enclosing shield 38 of electricallyconductive material; If support sheet 36 is made much thicker-thanspacing sheet 34, the capacitance between each coupling element 32 andshield 38 is efiectively negligible compared to that between the elementand winding 24.

Winding form 22 may typically comprise a piece of epoxy circuit board 1/16-inch thick. Winding 24 may be-close wound with No. 32 varnishinsulated copper wire, yielding about 100 turns perinch. With groundplane array 30 spaced by layer 34 about 0.010 of an inch from thewinding, a delay line eight inches long and four inches wide thenproduces a delay time of the order of l microsecond. Widely differentdelay times may be obtained in accordance with known electroma'gneticprinciples by varying the dimensions and ble for producing selectivelythe two letters A and C on a cathode ray tube 40. For each letter, onepair of strips X1 and X2 is employed for generating an X waveform fordriving the x-component of the cathode ray beam deflection, while asecond pair of strips Y1 and Y2 controls the y-component of thedeflection. A third pair of strips Z1 and Z2 controls the beamintensity. All strips are normally grounded via the switches of relaysRyA and RyC, which control the letters A and C. respectively. To displaya letter, the corresponding relay coil is energized by current suppliedfrom the selection circuit 42A or 42C, lifting ground from all stripsfor that letter and connecting them instead in pairs to the inputs ofamplifiers MX, MY and MZ. As indicated schematically, the respectiveamplifier outputs control the deflection voltages applied to the xandy-deflection plates 44 and the beam intensifying electrode 46 of thecathode ray tube. Separate beam positioning voltages, derived by knownmeansnot explicitly shown, are supplied to the deflection circuits todefine the location on the screen of each character.

The coupling strips of each pair have straight outer edges and areseparated from each other by a narrow slot 33. The widths of the twostrips of each pair then vary in mutually complementary fashion. Withthe two strips connected to the respective input terminals of adifferential amplifier the output waveform generated when the delay lineis energized by a sharp pulse E corresponds closely to the shape of slot33. The use of such strip pairs with complementary contours has theadvantage that the output waveform can readily be driven both above andbelow ground potential. For that purpose the contours need not bestrictly complementary, and departures from that relation may be usefulunder special conditions. I

The strip contours shown in FIG. 4 illustrate in principle how tworepresentative letters may be generated. The letter A is drawn in twostrokes, between which the beam is blanked to permit repositioning forthe second stroke. The letter C requires only one stroke, and thewaveform for the intensity control is then very simple. In principle,the Z strips can be designed to compensate the beam intensity on the CRTscreen for non-uniform deflection speed, but it is usually preferable toemploy the Z strips only for switching the beam on and off withoutproportional modulation. Uniform line intensity on the CRT screen isthen obtained'by designing the strip contours to produce uniformdeflection speed of the cathode ray beam along its path wheneverthe beamis not blanked. Alternatively, different strokes of a character, ordifferent characters may be traced with different intensity, if desired,by intentionally modifying the waveforms to produce appropriatevariations of beam velocity.

An alternative arrangement of coupling elements is shown in FIGS. 5 and6-for producing waveforms that extend both above and below groundpotential. Whereas thesystem of FIG. 4 provides two coupling elements ofcomplementary form that are coupled to a common delay line and supplytheir signals to opposite terminals of a difierential amplifier, thesystem of FIGS. 5 and 6 provides two delay lines that are energized bypulses of opposite polarity. Complementary coupling strips are coupledto the respective delay lines, and the charges on the two elements areadded to provide a single output signal.

. In the illustrative arrangement of FIG. 5, the two complementarycouplingelements 32a 32b are carried on opposite faces of a commondielectric board 36a.

That assembly is sandwiched between the two delayare typically connecteddirectly together through the support board, as indicated at 39, withthe common outputline 39a, may be connected by external circuitry. Inputenergizing pulses to the two delay lines are typically synchronized andof similar form but opposite polarity, as indicated at E1 and E2. FIG. 7,is a graph representing the type of output signal S corresponding toinputs E1 and E2 and to the illustrative coupling strip contours of FIG.6. Modified results may be obtained with the same structure by employingenergizing pulses that differ from each other in form, amplitude ortiming.

As an' alternative structure, the two distinct delay lines of FIG. 5maybe replaced by a single line of twice the length, suppliedsimultaneously with a positive input pulse. at one end and a negativepulse at the other end. A single strip shaped like 32a of FIG. 6 forhalf its length and like a mirror image of 345 the other half, will thengive an equivalent output.

FIG. 8 illustrates schematically the general manner in which the outputfrom a contoured coupling element, varies with different types of delayline energization and with different output circuit arrangements. The

In FIG. 9 the numeral 50 designates a data processing device whichproduces on the lines bl, b2 b7 a seven digit binary code representationof a character to be displayed, and at the same time I generates on theline 52 an energizing pulse, typically a sharp voltage pulse asindicated at E. The complete font of available characters is assumed forpurposes of diagram shows in section A an illustrative strip contour, V

waveform B. Sections D and E of FIG. 8 showthe waveforms obtained whenthe coupling strip is effectively grounded and the output signal isproportional to the currentto ground. Such a signal may be taken inprinciple as the voltage drop across a resistor to ground, as indicatedin the figure, or may be measured directly by a current responsiveamplifier.

FIG. 9 represents schematically an illustrative system for selecting anddisplaying characters under control of a code representation of thecharacter to be displayed. An important feature of the system shown isthe utilization of several distinct delay lines for different groups ofcharacters, so that selection of an individual character is carried outin two steps, typically under control of distinct digits of the completedigital code by which the characters are designated. One group of digitsdesignates the delay line associated with the desired character, anddirects an energizing pulse to that delay line; while another group ofdigits designates the particular character of the group associated withthat delay line, and effectively connects the coupling strips for thatcharacter to the output circuit. Thatdivision of selectionresponsibility greatly reduces the total number of switching elementsrequired for the entire selection function.

illustration to include 96 characters, of which'32 are generated by eachof the three delay lines indicated schematically at A, B and C. Forclarity of illustration, only the input terminal 29 to the winding andthe output'terminals 35 from selected strips are shown explicitly foreach delay line. Separate output terminals are indicated at X and Y forthe xand y-coordinates for each of the characters, which are numbered 1,2,-

32 each delay line. Additional coupling strips may be provided, asalready indicated, for controlling the beam intensity, but are omittedin FIG. 5 for clarity of illustration.

' The X output terminals for characters Al,'B1 and Cl.

are connected in parallel to the line DXl, and the X' output terminalsfor the correspondingv groups of characters with higher numbers aresimilarly connected to the respective lines DX2 to DX32. Those lines areconnected to ground through the collector-emitter circuits of therespective switching transistors OX1 to QX32. The Y output terminals forthe various characters are similarly connected to the lines DYl to DY32,which are connected to ground through the respective transistors QYl toQY32. Lines DX11to DX32 are also coupled via the respective capacitors CXl to C832 to the line 47X, which is connected directly as input to theamplifier MX. Lines DYl to DY32 are similarly couinput terminals via therespective switching transistors QA, OB and QC.

In order to control the switching transistors QA, QB, QC for the delaylines A, B and C and the transistors QXl to 0X32 and QYl to QY32 for theoutput strips, the binary digital representation b1 to b7 is firstdecoded by the decoding circuits 60, 62 and 64, which are typically ofconventional design and do not require detailed description. Decoder 60receives as input the binary digital signals for the three digits b1, b2and b3, which represent a particular one of eight possible values. Theeight output lines 0 to 7 fromdecoder 60 are normally maintained atpositive potential; In response to an input code signal thecorresponding output line becomes grounded. Decoder 62 similarlyreceives input signals for the two digits b4 and b5 and produces asoutput signal grounded condition of the corresponding one of the fouroutput lines 0 to 3, which are normally positive. The output lines fromdecoders 60 and 62 are coupled in matrix fashion via the summingresistances R3 to the output lines F1 to F32, according to thecharacters represented by the respec tive code configurations. Each lineF1 to- F32 is connected in parallel to the bases of both transistors QXand QY for the corresponding number 1 to 32. The values of resistors R3are selected so that each of those transistors is maintained conductivewhen at least one of the associated output lines from decoders 60 and 62is positive, and is cut off only when both those output lines aregrounded. Accordingly, all outputs from the three delay lines A, Band Care disabled except for those that are isolated from ground by cutoffcondition of the selected pair of transistors QX and QY, whichcorrespond to the code representation b1 to b5 supplied from data device50.

Decoder 64 receives as input the digital signals b6 and b7 and producesas output signal grounded condition of the corresponding one of theoutputlines A, B and C, which are normally positive. Those lines areconnected through the current limiting resistors R2A, R23 and R2C to thebases of the respective transistors QA, QB and QC. Accordingly,energizing pulse E reaches only the one delay line A, B or C.thatcorresponds to the code representation b6, b7. Those delay lines whichdo not receive an input pulse have no effect upon the ungrounded outputline DX or DY except for contributing a small capacitance to ground.

The overall operation of the selection circuit is thus to. deliver eachenergizing pulse E to' only one delay line, and to disable all outputsignals from that line except one set. The resulting output signalssupplied to the deflection electrodes 44 of cathode ray tube 40 producethe character represented by the code signals b1 to b7 FIG. illustratesa further aspect of the invention, by which a waveform generator of thegeneral type already described may be modified to expand the time baseof the resulting waveforms to any desired extent. The waveformgenerator, 70 includes the delay line winding 72 with input line 73 andterminating resistance R5. The two output elements of complementary form74a and74b are capacitively coupled to the delay line and to theamplifier M4, producing on the line 78 a waveform 75 with time basecorresponding directly to the delay time of the delay line. The twoadditional output elements 76a and 76b are coupled to the delay line andto the amplifier M6, producing the reference ramp function 77, whichrises uniformly throughout the duration of waveform 75 and in definitephase relation to it.

The system of FIG. 10 is set in operation by a control pulse on the line6 8. That pulse is supplied to the oscillator 71, which produces acontinuing series of pulses E of suitable form for periodicallyenergizing waveform generator 70. The control pulse on line 68 is alsosupplied to the ramp generator 80, which may be of conventional type andproduces on the line 84 the control ramp function 82, which hastypically the same total voltage rise as reference ramp 77, alreadydescribed. However, the time base of control ramp 82 is entirelyindependent of the delay time of delay line 72, and is selected inaccordance with the desired duration of the final output waveform.Control ramp 82 and reference ramp 77 are supplied as inputs to thecoincidence circuit 86. That circuit typically produces a square wavepulse whenever ramp 77 exceeds ramp 82, and differentiates the resultingsquare waves to produce a sharp positive pulse each time the rampscross. Those pulses 87 are supplied via the line 88 as control signalsto the gating circuit 90, which receives as input the original series ofwaveforms 75. In response to each control pulse 87, gate 90 supplies tooutput line 91 a voltage corresponding to the momentary value ofwaveform 75. Those output voltages are smoothed by lowpass filter 92,producing on the line 94 a reproduction 96 of waveform 75, but with itstime base expanded to correspond to the duration of control ramp 82. Thetime base expansion produced by the system is readily variable byadjustment of ramp generator 80, and may represent many orders ofmagnitude.

When a waveform generator in accordance with the present invention is tobe used for character generation the sampling technique representedillustratively in FIG. l0 provides useful flexibility. For example, a

character generator designed for a cathode ray tube using electrostaticbeam deflection canbe modified by time base expansion to produce awaveform duration appropriate for a cathode ray tube with magneticdeflection. Also, by providing time base expansion of several orders ofmagnitude, a character generator of the present type can effectivelydrive a'pen recorder having separate xand y-axis drives. Such recordersare employed in automatic drafting machines of known type, but thecharacter generating systems previously available for such machines tendto be extremely complex. By providing convenient and economicalcharacter generation for pen recorders and the like, the presentinvention permits great simplification of previously available automaticdrafting machines.

In accordance with a further aspect of the invention, an initialwaveform may be generated which represents modulation of a carrierfrequency by the desired final waveform. That initial waveform may thenbe demodulated to produce the desired final waveform. An advantage ofthat procedure is that a single coupling strip may be formed torepresent two fmal waveforms, bothmodulating the same carrier frequencybut in mutually displaced phase relation, as in conventional multiplexsignal transmission. The two desired waveforms can then be recoveredfrom the initially generated v waveform by phase sensitive demodulation,utilizing respective reference signals that have suitable phaserelations. Such reference phase signals can be generated in any suitablemanner, preferably by two additional coupling strips associated with thesame delay line that generates the initial waveform.

FIG. 11 represents schematically and in simplified form an illustrativesystem of the type just described. A delay line winding is indicated at24c with input pulse E and with an assembly 30c of coupling strips forgenerat ing three distinct waveforms A, B and C. The curves sodesignated in FIG. 11 show the shapes of the waveforms produced, and maybe considered to represent the forms of the gaps between respectivepairs of coupling strips, such as those of FIG. 4, the strips themselvesbeing omitted in FIG. 11 to simplify the drawing. Waveforms A and B areproduced on the output lines 96A and 968, respectively, and are suppliedas reference phase signals to the respective demodulators 98 and 99.

The reference phase signals A and B comprise sinusoidal waveforms ofconstant amplitude mutually produced from a single initial waveform. Thefirst half of waveform C is a sinusoidal curve of gradually decreasingamplitude in phase with reference wave A, while the second half of C hasgradually increasing amplitude in phase with B. Waveform C is suppliedvia the line 97 as input to both demodulators 98 and 99. Demodulator 98produces a waveform corresponding to the envelope of the component ofthe input signal in phase with reference A, as indicated in somewhatidealized form at 100. Demodulator 99 similarly responds only to thecomponent of the input in phase with reference B, as indicated at 102.Those two final waveforms l'and 102 can be employed, for example, todrive the xand y-deflection circuits of a cathode ray tube, producing onthe screen a letter L. The two phase components of waveform C are shownseparated in time for clarity of illustration, but in practice may, ofcourse, overlap in time.

I claim:

l. Mechanism for generating selectively individual continuous electricalwaveforms having respective predetermined waveform shapes, comprisingdelay line means including a delay line having an effectively flatsurface and means for energizing the delay line to produce electricalwave front propagation along the surface longitudinally of the delayline,

an array of elongated conductive strips mounted in a common planeparallel to the delay line surface with the strips extendinglongitudinally of the delay line and capacitively coupled thereto,

said strips being uniformly spaced from the delay line surface by asheet of dielectric material of a thickness that is uniform for allstrips,

a plurality of said strips having widths which vary progressively alongthe strip length in accordance with said respective waveform shapes,circuit means normally connecting the strips to a source of referencepotential to form a ground plane for the delay line, said circuit meansincluding switching mechanism for isolating selected strips of saidplurality from the potentialsource,

and output circuit means coupled to at least the so selected strips toreceive electrical signals therefrom in response to said wavefrontpropagation. t v

2. Mechanism as defined in claim 1, and in which a plurality of saidstrips are arranged in pairs of mutually adjacent strips withapproximately straight parallel outer edges and with inner edgesseparated by a slot of approximately constant width, the strips of eachpair having widths that vary in mutually complementary relation inaccordance with one of said predetermined waveform shapes,

and said output circuit means include means for combining the signalsreceived from the strips of a pair in opposite polarity to produce aunitary waveform.

3. Mechanism as defined in claim 1, and including means for periodicallyoperating said delay line energizing means to generate a periodic seriesof essentially identical wavgforms,

means or enving rom successive waveforms of said series signals thatrepresent the waveform amplitude at respective successive waveformportions,

and means for deriving from such signals a waveform of similar shape butexpanded time base.

4. Mechanism as defined in claim 1, and in which said width variationsof at least one strip correspond t omodulation of a carrier frequency bya predetermined waveform shape,

and said output circuit means include phase sensitive circuit means fordemodulating the initial waveform signal received from .said strip toproduce said waveform,

structure capacitively coupled to said delay line for generating areference phase signal having definite phase relation to said carrierfrequency,

and circuit means for supplying the phase signal as reference phase tothe demodulating circuit means.

1. Mechanism for generating selectively individual continuous electricalwaveforms having respective predetermined waveform shapes, comprisingdelay line means including a delay line having an effectively flatsurface and means for energizing the delay line to produce electricalwave front propagation along the surface longitudinally of the delayline, an array of elongated conductive strips mounted in a common planeparallel to the delay line surface with the strips extendinglongitudinally of the delay line and capacitively coupled thereto, saidstrips being uniformly spaced from the delay line surface by a sheet ofdielectric material of a thickness that is uniform for all strips, aplurality of said strips having widths which vary progressively alongthe strip length in accordance with said respective waveform shapes,circuit means normally connecting the strips to a source of referencepotential to form a ground plane for the delay line, said circuit meansincluding switching mechanism for isolating selected strips of saidplurality from the potential source, and output circuit means coupled toat least the so selected strips to receive electrical signals therefromin response to said wavefront propagation.
 2. Mechanism as defined inclaim 1, and in which a plurality of said strips are arranged in pairsof mutually adjacent strips with approximately straight parallel outeredges and with inner edges separated by a slot of approximately constantwidth, the strips of each pair having widths that vary in mutuallycomplementary relation in accordance with one of said predeterminedwaveform shapes, and said output circuit means include means forcombining the signals received from the strips of a pair in oppositepolarity to produce a unitary waveform.
 3. Mechanism as defined in claim1, and including means for periodically operating said delay lineenergizing means to generate a periodic series of essentially identicalwaveforms, means for deriving from successive waveforms of said seriessignals that represent the waveform amplitude at respective successivewaveform portions, and means for deriving from such signals a waveformof similar shape but expanded time base.
 4. Mechanism as defined inclaim 1, and in which said width variations of at least one stripcorrespond to modulation of a carrier frequency by a predeterminedwaveform shape, and said output circuit means include phase sensitivecircuit means for demodulating the initial waveform signal received fromsaid strip to produce said waveform, structure capacitively coupled tosaid delay line for generating a reference phase signal having definitephase relation to said carrier frequency, and circuit means forsupplying the phase signal as reference phase to the demodulatingcircuit means.